1. Field of the Invention
The present invention relates to a controller for controlling power source connections to a circuit in an electrical apparatus and a method thereof. More particularly, it relates to a power source connection controller for automatically disconnecting a power source of an electrical apparatus and returning from an automatic power-off state and a method thereof.
2. Description of Related Art
Microcomputers are included in various types of electrical apparatuses as an internal circuit. FIG. 8 shows an example of connection among a microcomputer 72, a power supply circuit 74, and control switches SW1, SW2, and SW3. The microcomputer 72 is connected to the power supply circuit 74 via a power source connecting switch SWPW. On closing the switch SWPW, a predetermined voltage is applied to the microcomputer 72. The circuit 74 converts and/or regulates a voltage supplied from a power source (not shown). A battery may be used for a power source. An ordinary plug socket wired within a house may be also used as a power source. In FIG. 8, the circuit 74 supplies a voltage E required for operation of the microcomputer 72 between terminals INp and Inn.
The microcomputer 72 shown in FIG. 8 has 3 inputs (I/O-1, I/O-2, and I/O-3) and one output (I/O-0). I/O-1 is connected to ground via the switch SW1. I/O-2 and I/O-3 are respectively connected to ground via the switches SW2 and SW3 as well. xe2x80x9cGroundxe2x80x9d is not always limited to a ground voltage level, but it may be any desired voltage level. SW1, SW2, and SW3 are push-button switches. The contacts S1c and S2d of SW1 are normally open, and closed while pressing SW1. The contacts S2c and S2d, and the contacts S3c and S3d are similarly closed while pressing the switches SW2 and SW3.
Predetermined functions (Function 1, Function 2, and Function 3) executable by a microcomputer are assigned to each control switch (SW1, SW2, and SW3). Since I/O-1 is connected to ground after SW1 is pressed, the microcomputer 72 detects that I/O-1 has been connected to the ground, and executes Function 1 assigned to SW1. Similarly, on pressing SW2 and SW3, the microcomputer 72 respectively executes Function 2 and Function 3. It is necessary to keep pressing a control switch for a predetermined time sufficient to allow the microcomputer 72 to recognize that the control switch has been pressed. Generally, keeping a press of a control switch for tens to hundreds milliseconds will be sufficient for the microcomputer 72 to recognize that the control switch has been pressed.
A power-off signal PWOFF for opening the power source connecting switch SWPW is outputted from I/O-0 of the microcomputer 72. If any of control switches SW1, SW2, and SW3, for example, have never been pressed within a predetermined time, the signal PWOFF is automatically sent from the microcomputer 72. If a predetermined time has elapsed since a control switch was pressed the last time, the power source is automatically shut off.
FIG. 8 illustrates closing and opening of the connecting switch SWPW between the power supply circuit 74 and the microcomputer 72. There may be a case where a connecting switch SWP1 is provided between a power source 76 and the power supply circuit 74 as shown in FIG. 9 (a) because actual electrical apparatus may include a device other than a microcomputer as well. In FIG. 9 (a), the power source 76 can be disconnected from an entire electrical apparatus 70 including the microcomputer 72 by opening SWP1. As shown in FIG. 9 (b), a connecting switch SWP2 between the circuit 74 and other device 80 may be opened and closed. In FIG. 9 (b), the other device 80 is disconnected from the circuit 74 by opening only SWP2, so that the microcomputer 72 may remain connected to the circuit 74.
In FIG. 9 (a), the switch SWP1 for connecting the power source 76 to the power supply circuit 74 for supplying a required voltage to the microcomputer 72 and other device 80 is opened by the power-off signal PWOFF sent from the microcomputer 72. After SWP1 is opened, power supply to the entire electrical apparatus including the microcomputer 72 is cut off Power consumption of the electrical apparatus 70 at this time is zero. When operation is not performed for a predetermined time, it is possible to prevent power consumption by automatically disconnecting the power source 76. However, the power supply needs to be reconnected to operate the electrical apparatus 70 again because the power source 76 is completely turned off. It is necessary to close the switch SWP1 by the power switch SWPW before pressing the control switches SW1, SW2, and SW3.
In FIG. 9 (b), the switch SWP2 for connecting the power supply circuit 74 to other device 80 is opened by a power-off signal PWOFF from the microcomputer 72. Upon opening of SWP2, power supply to other device 80 is shut off. Since SWP1 for connecting the power source 76 to the power supply circuit 74 keeps closed, a required voltage is supplied from the circuit 74 to the microcomputer 72. The power consumption of an electrical apparatus 78 in this case does not become zero because the circuit 74 and the microcomputer 72 consume power. On pressing SW1, SW2 or SW3, the microcomputer 72 automatically closes SWP2 to enable other device 80 and performs the function assigned to the pressed manipulation switch button. It is not necessary to turn on the power source afresh like the electrical apparatus 70 shown in FIG. 9 (a), but in FIG. 9 (b), the power consumption does not become zero due to continued power supply to the microcomputer 72.
It is an object of the present invention to provide a technique which can reduce power consumption of an electrical apparatus by an automatic power-off and in addition can perform easily and quickly return from the automatic power-off state. A power source connection controller according to the present invention comprises: (a) a power source connecting switch connected between a power source and an internal circuit of an electrical apparatus; (b) means for controlling opening and closing of the power source connecting switch, the controlling means being connected between the power source and the power source connecting switch; (c) a first switch for inputting a signal to the internal circuit to provide instructions for executing a predetermined function provided for the electrical apparatus; and (d) a second switch for causing the controlling means to close the power source connecting switch, the second switch being connected between the power source and the controlling means, the first and second switches operating jointly. Upon receipt of a power-off signal from the internal circuit, the controlling means releases the power source connecting switch from closed state. The power source connection controlling method according to the present invention includes the steps of: providing instructions for an internal circuit to execute a predetermined function provided for the electrical apparatus, while the power source is shut off, connecting the power source to the internal circuit in synchronization with the instruction to the internal circuit; and allowing the internal circuit to execute the predetermined function after the power source is connected to the internal circuit. The power source connection controlling method further includes a step of disconnecting the power source from the internal circuit in response to the power-off signal, from the internal circuit.
According to the present invention, when control switches are not pressed for a predetermined time or longer, power consumption can be reduced to zero by automatically cutting off a power source. When an electrical apparatus is not in active use, its power consumption can be reduced. Even if the power source is in a power-off state, the power source is automatically turned on by pressing a control switch, and then a microcomputer is actuated. An easy and quick return from the automatic power-off state is possible. Users can carry out operations without being conscious of ON/OFF of the power source.